The present invention relates to a push button type switch, wherein the pressing element retains in an initial position despite the condition of the switch so as to be formed as a complete opening and closing loop.
The push button type switch of the current electronic products, as shown in FIGS. 1A and 1B, has a casing with a control rod slidable in the casing. An elastic element is installed between the control rod and an end surface of the casing. A plurality of confining blocks as a sliding guiding surface is formed on the control rod so as to be formed as a track guide. An elastomer displacing along the track guide is formed on the control rod. The control rod moves downward to press the elastic element and then to drive the elastomer to be moved along the track guide to a center confining block for positioning thereon. A driven piece connected to another end of the control rod will press contact pieces to cause terminals to be conductive, and then a force is applied to the control rod again so that it is moved along the track guide to the initial position. Then, the driven piece is driven synchronously to separate from a pressing position of the contact piece, and thus, the circuit is opened. However, the prior art push button type switch has the following disadvantages:
1. The parts of the push button type switch can not be easily assembled. As the elastomer moves in the track guide, the confining blocks are often worn so that the elastomer will deform or the confining block wears so that as the control rod is pressed downwards, the control rod can not substantially press the contact piece for controlling the opening and closing of the switch.
2. As the control rod is depressed to be positioned in the confining block, it can not restore to the initial condition, while at next time, as it is pressed for restoring to the initial condition, the switch is opened. Therefore, the operation is inconvenient. The push button type switch has on displaying device. The user can not determine the condition of the switch. Moreover, the contact piece is made of a single metal piece with only one thermal extension coefficient. Thus, the object of overload protection can not achieve. As a result, the applications are confined.
Accordingly, the primary object of the present invention is to provide a push button type switch, wherein the pressing element retains in an initial position despite the condition of the switch so as to be formed as a complete opening and closing loop.
Another object of the present invention is to provide a push button type switch, wherein a display lamp set is further installed for informing the user the condition of the current switch.
A further object of the present invention is to provide a push button type switch, wherein the contact piece is formed by two metal pieces with different extension coefficients for achieving the effect of over current or over voltage protection.